Computation of Leave. 1. The anniversary date of the employee’s contract of employment shall be used for the purpose of computing the amount of vacation leave to which the employee is entitled to accrue. Employees working less than twelve (12) months per year who have or will bid into a twelve (12) month position shall use the following formula to determine the amount of vacation they are entitled to accrue when entering the twelve (12) month position: [number of years employed] X [months worked per year] ÷ 12= years of service].